The grey-scale background map displays the JVLA 3 GHz radio continuum emission within the halo of NGC 4217 at 7′′ angular answer. Credit score: Heesen et al., 2024.
A global crew of astronomers has carried out radio observations of a star-forming galaxy referred to as NGC 4217. The observational marketing campaign detected a big radio bubble within the galaxy’s halo. The discovering used to be reported in a paper revealed September 23 at the pre-print server arXiv.
Positioned some 61.6 million mild years away, NGC 4217 is a close-by edge-on star-forming spiral galaxy. Earlier observations of this galaxy have discovered that it incorporates dozens of soaking up mud buildings with quite a lot of morphologies. Additionally, a radio halo extending to about 16,000 mild years from the galaxy’s star-forming disk has been known.
Not too long ago, a gaggle of astronomers led by way of Volker Heesen of Hamburg College in Germany, has hired the Jansky Very Massive Array (JVLA) and with LOw Frequency ARray (LOFAR), to take a better have a look at NGC 4217 in radio band.
“We provide new observations of the CHANG-ES [Continuum HAloes in Nearby Galaxies—an EVLA Survey] galaxy NGC 4217 in S-band (2–4 GHz) which we mix with archival LoTSS-DR2 [LOFAR Two-metre Sky Survey data release 2] information at 144 MHz,” the researchers wrote within the paper.
The observations detected a conspicuous extension of radio continuum emission within the north-western halo of NGC 4217. Additional inspection of this emission allowed Heesen’s crew to spot an excessively prolonged faint element that had in the past avoided detection.
The pictures display that this element has the morphology of an edge-brightened bubble extending out to a distance of 65,000 mild years from the star-forming disk.
In line with the paper, the emission is boosted alongside the partitions of NGC 4217’s radio bubble with a slight melancholy within the heart of the bubble. The northeastern fringe of the bubble is specifically distinguished and the accumulated pictures counsel the prospective presence of a shell in this facet.
The learn about discovered that the dimensions heights of the radio bubble are 19,200 and 9,400 mild years, at 144 MHz and three GHz, respectively. Due to this fact, they’re a couple of instances greater than the standard scale heights of radio bubbles in edge-on galaxies. The full magnetic box energy of the bubble in NGC 4217 used to be measured to be about 11 µG.
Moreover, the astronomers estimated that on the fringe of the bubble, the wind velocity rises from roughly 300 to 600 km/s, which is roughly at a degree of the get away speed of NGC 4217.
This end result means that the bubble may also be inflated by way of about 10% of the kinetic power injected by way of supernovae over its dynamical time-scale of 35,000 years. Alternatively, the researchers word that now not the entire kinetic power can be utilized to inflate the bubble as huge fractions is also radiated away.
Additional info:
V. Heesen et al, CHANG-ES XXXIV: a 20 kpc radio bubble within the halo of the star-forming galaxy NGC 4217, arXiv (2024). DOI: 10.48550/arxiv.2409.15449
Magazine knowledge:
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